Summary of the Project Pediatric cataract is the most common form of childhood blindness and is both clinically and genetically heterogeneous. Autosomal dominant and recessive forms of cataract have been reported to be caused by mutations in nearly 22 different genes so far. More than half of the muitants occur in crystallins, in A- and B-crystallins mostly. This proposal is aimed to investigate the possibility that mutations in A- and B-crystallins cause cataract by introducing significant conformational changes which will initiate a cascade of events leading to dysfunctional molecular chaperones lacking the ability to interact with native A- and B-crystallins and the various protein substrates. For this study, we have selected 8 mutants of A-crystallin and 4 mutants of B-crystallin, all known to be responsible for congenital cataracts. We will study 1) the structural, functional and hydrodynamic properties of these mutants in the homooligomeric and heterooligomeric forms (Aims 1 & 2), 2) the interaction of the mutants with A-wt and B-wt by using FRET in an in vitro system (Aim 3), and 3) study the expression of the mutants and their interaction with A-wt and B-wt using FRET and asses the presence of protein aggregates, while each mutant is expressed alone or co-expressed with A-wt or B-wt in mammalian cells. These studies are expected to show the underlying mechanism by which various mutants cause cataract in the affected individuals.